Methane Conversion Apparatus and Process Using a Supersonic Flow Reactor

ABSTRACT

Apparatus and methods are provided for converting methane in a feed stream to acetylene. A hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application No.61/691,303 filed Aug. 21, 2012, the contents of which are herebyincorporated by reference in its entirety.

FIELD

Apparatus and methods are disclosed for converting methane in ahydrocarbon stream to acetylene using a supersonic flow reactor.

BACKGROUND

Light olefin materials, including ethylene and propylene, represent alarge portion of the worldwide demand in the petrochemical industry.Light olefins are used in the production of numerous chemical productsvia polymerization, oligomerization, alkylation and other well-knownchemical reactions. These light olefins are essential building blocksfor the modern petrochemical and chemical industries. Producing largequantities of light olefin material in an economical manner, therefore,is a focus in the petrochemical industry. The main source for thesematerials in present day refining is the steam cracking of petroleumfeeds.

The cracking of hydrocarbons brought about by heating a feedstockmaterial in a furnace has long been used to produce useful products,including for example, olefin products. For example, ethylene, which isamong the more important products in the chemical industry, can beproduced by the pyrolysis of feedstocks ranging from light paraffins,such as ethane and propane, to heavier fractions such as naphtha.Typically, the lighter feedstocks produce higher ethylene yields (50-55%for ethane compared to 25-30% for naphtha); however, the cost of thefeedstock is more likely to determine which is used. Historically,naphtha cracking has provided the largest source of ethylene, followedby ethane and propane pyrolysis, cracking, or dehydrogenation. Due tothe large demand for ethylene and other light olefinic materials,however, the cost of these traditional feeds has steadily increased.

Energy consumption is another cost factor impacting the pyrolyticproduction of chemical products from various feedstocks. Over the pastseveral decades, there have been significant improvements in theefficiency of the pyrolysis process that have reduced the costs ofproduction. In a typical or conventional pyrolysis plant, a feedstockpasses through a plurality of heat exchanger tubes where it is heatedexternally to a pyrolysis temperature by the combustion products of fueloil or natural gas and air. One of the more important steps taken tominimize production costs has been the reduction of the residence timefor a feedstock in the heat exchanger tubes of a pyrolysis furnace.Reduction of the residence time increases the yield of the desiredproduct while reducing the production of heavier by-products that tendto foul the pyrolysis tube walls. However, there is little room left toimprove the residence times or overall energy consumption in traditionalpyrolysis processes.

More recent attempts to decrease light olefin production costs includeutilizing alternative processes and/or feed streams. In one approach,hydrocarbon oxygenates and more specifically methanol or dimethylether(DME) are used as an alternative feedstock for producing light olefinproducts. Oxygenates can be produced from available materials such ascoal, natural gas, recycled plastics, various carbon waste streams fromindustry and various products and by-products from the agriculturalindustry. Making methanol and other oxygenates from these types of rawmaterials is well established and typically includes one or moregenerally known processes such as the manufacture of synthesis gas usinga nickel or cobalt catalyst in a steam reforming step followed by amethanol synthesis step at relatively high pressure using a copper-basedcatalyst.

Once the oxygenates are formed, the process includes catalyticallyconverting the oxygenates, such as methanol, into the desired lightolefin products in an oxygenate to olefin (OTO) process. Techniques forconverting oxygenates, such as methanol to light olefins (MTO), aredescribed in U.S. Pat. No. 4,387,263, which discloses a process thatutilizes a catalytic conversion zone containing a zeolitic typecatalyst. U.S. Pat. No. 4,587,373 discloses using a zeolitic catalystlike ZSM-5 for purposes of making light olefins. U.S. Pat. Nos.5,095,163; 5,126,308 and 5,191,141 on the other hand, disclose an MTOconversion technology utilizing a non-zeolitic molecular sieve catalyticmaterial, such as a metal aluminophosphate (ELAPO) molecular sieve. OTOand MTO processes, while useful, utilize an indirect process for forminga desired hydrocarbon product by first converting a feed to an oxygenateand subsequently converting the oxygenate to the hydrocarbon product.This indirect route of production is often associated with energy andcost penalties, often reducing the advantage gained by using a lessexpensive feed material.

Recently, attempts have been made to use pyrolysis to convert naturalgas to ethylene. U.S. Pat. No. 7,183,451 discloses heating natural gasto a temperature at which a fraction is converted to hydrogen and ahydrocarbon product such as acetylene or ethylene. The product stream isthen quenched to stop further reaction and subsequently reacted in thepresence of a catalyst to form liquids to be transported. The liquidsultimately produced include naphtha, gasoline, or diesel. While thismethod may be effective for converting a portion of natural gas toacetylene or ethylene, it is estimated that this approach will provideonly about a 40% yield of acetylene from a methane feed stream. While ithas been identified that higher temperatures in conjunction with shortresidence times can increase the yield, technical limitations preventfurther improvement to this process in this regard.

While the foregoing traditional pyrolysis systems provide solutions forconverting ethane and propane into other useful hydrocarbon products,they have proven either ineffective or uneconomical for convertingmethane into these other products, such as, for example ethylene. WhileMTO technology is promising, these processes can be expensive due to theindirect approach of forming the desired product. Due to continuedincreases in the price of feeds for traditional processes, such asethane and naphtha, and the abundant supply and corresponding low costof natural gas and other methane sources available, for example the morerecent accessibility of shale gas, it is desirable to providecommercially feasible and cost effective ways to use methane as a feedfor producing ethylene and other useful hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of a supersonic reactor inaccordance with various embodiments described herein;

FIG. 2 is a schematic view of a system for converting methane intoacetylene and other hydrocarbon products in accordance with variousembodiments described herein; and

FIG. 3 is a side cross-sectional view of a supersonic reactor inaccordance with various embodiments described herein.

FIG. 4 is a schematic view of a system for heat transfer between a heatexchanger and a downstream zone.

FIG. 5 is a side cross-sectional view of a straight single pass tubeconfiguration in accordance with various embodiments described herein.

FIG. 6 is a side cross-sectional view of a U-tube configuration inaccordance with various embodiments described herein.

DETAILED DESCRIPTION

One proposed alternative to the previous methods of producing olefinsthat has not gained much commercial traction includes passing ahydrocarbon feedstock into a supersonic reactor and accelerating it tosupersonic speed to provide kinetic energy that can be transformed intoheat to enable an endothermic pyrolysis reaction to occur. Variations ofthis process are set out in U.S. Pat. Nos. 4,136,015 and 4,724,272, andRussian Patent No. SU 392723A. These processes include combusting afeedstock or carrier fluid in an oxygen-rich environment to increase thetemperature of the feed and accelerate the feed to supersonic speeds. Ashock wave is created within the reactor to initiate pyrolysis orcracking of the feed.

More recently, U.S. Pat. Nos. 5,219,530 and 5,300,216 have suggested asimilar process that utilizes a shock wave reactor to provide kineticenergy for initiating pyrolysis of natural gas to produce acetylene.More particularly, this process includes passing steam through a heatersection to become superheated and accelerated to a nearly supersonicspeed. The heated fluid is conveyed to a nozzle which acts to expand thecarrier fluid to a supersonic speed and lower temperature. An ethanefeedstock is passed through a compressor and heater and injected bynozzles to mix with the supersonic carrier fluid to turbulently mixtogether at a speed of about Mach 2.8 and a temperature of about 427 C.The temperature in the mixing section remains low enough to restrictpremature pyrolysis. The shockwave reactor includes a pyrolysis sectionwith a gradually increasing cross-sectional area where a standing shockwave is formed by back pressure in the reactor due to flow restrictionat the outlet. The shock wave rapidly decreases the speed of the fluid,correspondingly rapidly increasing the temperature of the mixture byconverting the kinetic energy into heat. This immediately initiatespyrolysis of the ethane feedstock to convert it to other products. Aquench heat exchanger then receives the pyrolized mixture to quench thepyrolysis reaction.

Methods and apparatus for converting hydrocarbon components in methanefeed streams using a supersonic reactor are generally disclosed. As usedherein, the term “methane feed stream” includes any feed streamcomprising methane. The methane feed streams provided for processing inthe supersonic reactor generally include methane and form at least aportion of a process stream. The apparatus and methods presented hereinconvert at least a portion of the methane to a desired producthydrocarbon compound to produce a product stream having a higherconcentration of the product hydrocarbon compound relative to the feedstream.

The term “hydrocarbon stream” as used herein refers to one or morestreams that provide at least a portion of the methane feed streamentering the supersonic reactor as described herein or are produced fromthe supersonic reactor from the methane feed stream, regardless ofwhether further treatment or processing is conducted on such hydrocarbonstream. With reference to the example illustrated in FIG. 2, the“hydrocarbon stream” may include the methane feed stream 1, a supersonicreactor effluent stream 2, a desired product stream 3 exiting adownstream hydrocarbon conversion process or any intermediate orby-product streams formed during the processes described herein. Thehydrocarbon stream may be carried via a process stream line 115, asshown in FIG. 2, which includes lines for carrying each of the portionsof the process stream described above. The term “process stream” as usedherein includes the “hydrocarbon stream” as described above, as well asit may include a carrier fluid stream, a fuel stream 4, an oxygen sourcestream 6, or any streams used in the systems and the processes describedherein. The process stream may be carried via a process stream line 115,which includes lines for carrying each of the portions of the processstream described above. As illustrated in FIG. 2, any of methane feedstream 1, fuel stream 4, and oxygen source stream 6, may be preheated,for example, by one or more heaters 7.

Prior attempts to convert light paraffin or alkane feed streams,including ethane and propane feed streams, to other hydrocarbons usingsupersonic flow reactors have shown promise in providing higher yieldsof desired products from a particular feed stream than other moretraditional pyrolysis systems. Specifically, the ability of these typesof processes to provide very high reaction temperatures with very shortassociated residence times offers significant improvement overtraditional pyrolysis processes. It has more recently been realized thatthese processes may also be able to convert methane to acetylene andother useful hydrocarbons, whereas more traditional pyrolysis processeswere incapable or inefficient for such conversions.

The majority of previous work with supersonic reactor systems, however,has been theoretical or research based, and thus has not addressedproblems associated with practicing the process on a commercial scale.In addition, many of these prior disclosures do not contemplate usingsupersonic reactors to effectuate pyrolysis of a methane feed stream,and tend to focus primarily on the pyrolysis of ethane and propane. Oneproblem that has recently been identified with adopting the use of asupersonic flow reactor for light alkane pyrolysis, and morespecifically the pyrolysis of methane feeds to form acetylene and otheruseful products therefrom, is the very large amount of heat that isproduced in the supersonic reactor. In order to generate a large amountof heat and flowrate of the carrier fluid, a large amount of fuel isconsumed. Further, at least a portion of the heat must be removed fromthe process stream after pyrolysis occurs in order to halt the reactionwhen the desired products have been produced in so that the reactoreffluent and other streams may be sent downstream of the supersonicreactor. Moreover, additional heat may be required to preheat a fuelstream or a feed stream. Thus, it would be desirable, to reduce theamount of fuel and/or energy consumed by the supersonic reactor and toimprove the overall efficiency thereof Previous work has not fullyappreciated or addressed these concerns.

In addition, a carrier stream and feed stream may travel through thereactor at supersonic speeds, which can quickly erode many materialsthat could be used to form the reactor shell, even after a short amountof time. Moreover, certain substances and contaminants that may bepresent in the hydrocarbon stream can cause corrosion, oxidation, and/orreduction of the reactor walls or shell and other equipment orcomponents of the reactor. Such components causing corrosion, oxidation,or reduction problems may include, for example hydrogen sulfide, water,methanethiol, arsine, mercury vapor, carbidization via reaction with thefuel itself, or hydrogen embrittlement.

In accordance with various embodiments disclosed herein, therefore,apparatus and methods for converting methane in hydrocarbon streams toacetylene and other products is provided. Apparatus in accordanceherewith, and the use thereof, have been identified to improve theoverall process for the pyrolysis of light alkane feeds, includingmethane feeds, to acetylene and other useful products.

In accordance with one approach, the apparatus and methods disclosedherein are used to treat a hydrocarbon process stream to convert atleast a portion of methane in the hydrocarbon process stream toacetylene. The hydrocarbon process stream described herein includes themethane feed stream provided to the system, which includes methane andmay also include ethane or propane. The methane feed stream may alsoinclude combinations of methane, ethane, and propane at variousconcentrations and may also include other hydrocarbon compounds as wellas contaminants. In one approach, the hydrocarbon feed stream includesnatural gas. The natural gas may be provided from a variety of sourcesincluding, but not limited to, gas fields, oil fields, coal fields,fracking of shale fields, biomass, and landfill gas. In anotherapproach, the methane feed stream can include a stream from anotherportion of a refinery or processing plant. For example, light alkanes,including methane, are often separated during processing of crude oilinto various products and a methane feed stream may be provided from oneof these sources. These streams may be provided from the same refineryor different refinery or from a refinery off gas. The methane feedstream may include a stream from combinations of different sources aswell.

In accordance with the processes and systems described herein, a methanefeed stream may be provided from a remote location or at the location orlocations of the systems and methods described herein. For example,while the methane feed stream source may be located at the same refineryor processing plant where the processes and systems are carried out,such as from production from another on-site hydrocarbon conversionprocess or a local natural gas field, the methane feed stream may beprovided from a remote source via pipelines or other transportationmethods. For example a feed stream may be provided from a remotehydrocarbon processing plant or refinery or a remote natural gas field,and provided as a feed to the systems and processes described herein.Initial processing of a methane stream may occur at the remote source toremove certain contaminants from the methane feed stream. Where suchinitial processing occurs, it may be considered part of the systems andprocesses described herein, or it may occur upstream of the systems andprocesses described herein. Thus, the methane feed stream provided forthe systems and processes described herein may have varying levels ofcontaminants depending on whether initial processing occurs upstreamthereof.

In one example, the methane feed stream has a methane content rangingfrom about 65 mol-% to about 100 mol-%. In another example, theconcentration of methane in the hydrocarbon feed ranges from about 80mol-% to about 100 mol-% of the hydrocarbon feed. In yet anotherexample, the concentration of methane ranges from about 90 mol-% toabout 100 mol-% of the hydrocarbon feed.

In one example, the concentration of ethane in the methane feed rangesfrom about 0 mol-% to about 35 mol-% and in another example from about 0mol-% to about 10 mol-%. In one example, the concentration of propane inthe methane feed ranges from about 0 mol-% to about 5 mol-% and inanother example from about 0 mol-% to about 1 mol-%.

The methane feed stream may also include heavy hydrocarbons, such asaromatics, paraffinic, olefinic, and naphthenic hydrocarbons. Theseheavy hydrocarbons if present will likely be present at concentrationsof between about 0 mol-% and about 100 mol-%. In another example, theymay be present at concentrations of between about 0 mol-% and 10 mol-%and may be present at between about 0 mol-% and 2 mol-%.

The apparatus and method for forming acetylene from the methane feedstream described herein utilizes a supersonic flow reactor forpyrolyzing methane in the feed stream to form acetylene. The supersonicflow reactor may include one or more reactors capable of creating asupersonic flow of a carrier fluid and the methane feed stream andexpanding the carrier fluid to initiate the pyrolysis reaction. In oneapproach, the process may include a supersonic reactor as generallydescribed in U.S. Pat. No. 4,724,272, which is incorporated herein byreference, in its entirety. In another approach, the process and systemmay include a supersonic reactor such as described as a “shock wave”reactor in U.S. Pat. Nos. 5,219,530 and 5,300,216, which areincorporated herein by reference, in their entirety. In yet anotherapproach, the supersonic reactor described as a “shock wave” reactor mayinclude a reactor such as described in “Supersonic Injection and Mixingin the Shock Wave Reactor” Robert G. Cerff, University of WashingtonGraduate School, 2010.

While a variety of supersonic reactors may be used in the presentprocess, an exemplary reactor 5 is illustrated in FIG. 1. Referring toFIG. 1, the supersonic reactor 5 includes a reactor vessel 10 generallydefining a reactor chamber 15. While the reactor 5 is illustrated as asingle reactor, it should be understood that it may be formed modularlyor as separate vessels. If formed modularly or as separate components,the modules or separate components of the reactor may be joined togetherpermanently or temporarily, or may be separate from one another withfluids contained by other means, such as, for example, differentialpressure adjustment between them. A combustion zone or chamber 25 isprovided for combusting a fuel to produce a carrier fluid with thedesired temperature and flowrate. The reactor 5 may optionally include acarrier fluid inlet 20 for introducing a supplemental carrier fluid intothe reactor. One or more fuel injectors 30 are provided for injecting acombustible fuel, for example hydrogen, into the combustion chamber 25.The same or other injectors may be provided for injecting an oxygensource into the combustion chamber 25 to facilitate combustion of thefuel. The fuel and oxygen are combusted to produce a hot carrier fluidstream typically having a temperature of from about 1200 to about 3500 Cin one example, between about 2000 and about 3500 C in another example,and between about 2500 and about 3200 C in yet another example. It isalso contemplated herein to produce the hot carrier fluid stream byother known methods, including non-combustion methods. According to oneexample the carrier fluid stream has a pressure of about 1 atm orhigher, greater than about 2 atm in another example, and greater thanabout 4 atm in another example.

The hot carrier fluid stream from the combustion zone 25 is passedthrough a supersonic expander 51 that includes a converging-divergingnozzle 50 to accelerate the flowrate of the carrier fluid to above aboutmach 1.0 in one example, between about mach 1.0 and mach 4.0 in anotherexample, and between about mach 1.5 and 3.5 in another example. In thisregard, the residence time of the fluid in the reactor portion of thesupersonic flow reactor is between about 0.5-100 ms in one example,about 1.0-50 ms in another example, and about 1.5-20 ms in anotherexample. The temperature of the carrier fluid stream through thesupersonic expander by one example is between about 1000 C and about3500 C, between about 1200 C and about 2500 C in another example, andbetween about 1200 C and about 2000 C in another example.

A feedstock inlet 40 is provided for injecting the methane feed streaminto the reactor 5 to mix with the carrier fluid. The feedstock inlet 40may include one or more injectors 45 for injecting the feedstock intothe nozzle 50, a mixing zone 55, a diffuser zone 60, or a reaction zoneor chamber 65. The injector 45 may include a manifold, including forexample a plurality of injection ports or nozzles for injecting the feedinto the reactor 5.

In one approach, the reactor 5 may include a mixing zone 55 for mixingof the carrier fluid and the feed stream. In one approach, asillustrated in FIG. 1, the reactor 5 may have a separate mixing zone,between for example the supersonic expander 51 and the diffuser zone 60,while in another approach, the mixing zone is integrated into thediffuser section is provided, and mixing may occur in the nozzle 50,expansion zone 60, or reaction zone 65 of the reactor 5. An expansionzone 60 includes a diverging wall 70 to produce a rapid reduction in thevelocity of the gases flowing therethrough, to convert the kineticenergy of the flowing fluid to thermal energy to further heat the streamto cause pyrolysis of the methane in the feed, which may occur in theexpansion section 60 and/or a downstream reaction section 65 of thereactor. The fluid is quickly quenched in a quench zone 72 to stop thepyrolysis reaction from further conversion of the desired acetyleneproduct to other compounds. Spray bars 75 may be used to introduce aquenching fluid, for example water or steam into the quench zone 72.

The reactor effluent exits the reactor via outlet 80 and as mentionedabove forms a portion of the hydrocarbon stream. The effluent willinclude a larger concentration of acetylene than the feed stream and areduced concentration of methane relative to the feed stream. Thereactor effluent stream may also be referred to herein as an acetylenestream as it includes an increased concentration of acetylene. Theacetylene stream may be an intermediate stream in a process to formanother hydrocarbon product or it may be further processed and capturedas an acetylene product stream. In one example, the reactor effluentstream has an acetylene concentration prior to the addition of quenchingfluid ranging from about 2 mol-% to about 30 mol-%. In another example,the concentration of acetylene ranges from about 5 mol-% to about 25mol-% and from about 8 mol-% to about 23 mol-% in another example.

The reactor vessel 10 includes a reactor shell 11. It should be notedthat the term “reactor shell” refers to the wall or walls forming thereactor vessel, which defines the reactor chamber 15. The reactor shell11 will typically be an annular structure defining a generally hollowcentral reactor chamber 15. The reactor shell 11 may include a singlelayer of material, a single composite structure or multiple shells withone or more shells positioned within one or more other shells. Thereactor shell 11 also includes various zones, components, and ormodules, as described above and further described below for thedifferent zones, components, and or modules of the supersonic reactor 5.The reactor shell 11 may be formed as a single piece defining all of thevarious reactor zones and components or it may be modular, withdifferent modules defining the different reactor zones and/orcomponents.

By one approach, as illustrated in FIG. 3, at least one heat exchanger200 is provided for transferring heat from at least a portion of thesupersonic reactor pyrolysis or effluent stream to one or more otherportions of the process stream. The process stream may include any ofthe process streams described above, or may include other processstreams, including, for example, dedicated heat transfer processstreams. The dedicated heat transfer process streams may comprise anyphase or combination of phases, as further described herein.

In one approach, the heat exchanger 200 may be generally downstream ofthe supersonic reactor 5 such that a reactor effluent line carrying atleast a portion of the reactor effluent provides fluid to the heatexchanger 200. In another approach, the heat exchanger 200 may beintegrated with the supersonic reactor 5, including adding a portionthereof within the reactor chamber. In this approach, with reference toFIGS. 5 and 6, the heat exchanger 200 may include a stab-in heatexchanger 500. The stab-in heat exchanger 500 may include any number oftubes and tube configurations, including, but not limited to, straightsingle pass 505 as shown in FIG. 5, U-tube as shown in FIG. 6, coils, orother configurations, and combinations thereof In this regard, the heatexchanger 200 or a portion thereof may be positioned within variouslocations of the supersonic reactor, including, for example, within thereaction zone 65 or the quench zone 70 to transfer heat from at leastone of the pyrolysis stream and the effluent stream flowing through thereactor chamber 15. The stab-in heat exchanger includes a heat transferfluid flowing therethrough. The heat transfer fluid may include variousheat transfer fluids known in the art, including, but not limited tomolten metal, raising stream, superheating steam, hot oil, and liquidsodium

By one approach, in order to withstand harsh operating conditions withinthe reactor chamber 15, at least a portion of the heat exchanger mayinclude a ceramic tube heat exchanger. In one approach, the ceramic tubeheat exchanger comprises a material selected from the group of acarbide, a nitride, titanium diboride, a sialon ceramic, zirconia, orthoria. In another approach, the heat exchanger 200 includes highlyinert coated tubes to restrict corrosion of the tubes within the reactorchamber 15. In one approach, the highly-inert tubes includehighly-sulfided tubes that are formed by sulfiding. In another approach,the highly-inert tubes include carbon-carbon tubes. Carbon-carbon tubesmay be formed by providing a carbon coating on one or more tubes.

In one approach, the heat exchanger 200 includes tubes formed of amaterial having a melting temperature of above at least 800 C. To thisend, the tubes may be formed of a superalloy. In another approach, thetubes may be formed of nickel-based high-temperature low creepsuperalloy and chromium.

With reference to FIG. 4, in another approach, the heat exchanger 200provides heat to a circulating heat exchange fluid 310. In one example,the heat exchanger 200 includes a transport bed heat exchanger fortransferring heat between one or more fluid streams as described aboveand a high heat capacity bulk solid 310 flowing through the heatexchanger 200. Referring to FIG. 4, the transport bed heat exchanger 200may include direct heat exchange in which at least one of the pyrolysisstream and the effluent stream directly contacts the bulk solid materialto provide a heated bulk solid 320. In another approach, the transportbed heat exchanger may include indirect heat exchange in which at leastone of a pyrolysis stream and an effluent stream flows through one setof passageways of the heat exchanger 200 and a bulk solid material flowsthrough another set of passageways of the heat exchanger 200 so thatheat is transferred from the pyrolysis stream and/or the effluent streamto the bulk solid through components of the heat exchanger to providethe heated bulk solid 320. The heated bulk solid material 320 may thenbe transferred to another downstream zone 300 wherein the heat isrecovered or utilized. The bulk solid may then be returned to the heatexchanger 200 via line 350.

In another approach, the heat exchanger 200 includes a thermoelectricheat exchanger for converting a portion of the heat from one of thepyrolysis stream and the effluent stream to electricity. Thethermoelectric heat exchanger may include a high temperaturethermoelectric heat exchanger for operating in the presence of hightemperature fluids.

In another approach, the heat exchanger 200 may use a phasetransformation fluid capable of transferring energy from the one of thepyrolysis stream and the effluent stream to the phase transformationfluid by transformation of the phase thereof. In one approach, the phasetransformation fluid includes a eutectic-eutectic fluid capable of phasetransformation upon receiving energy from the pyrolysis stream or theeffluent stream. The eutectic-eutectic fluid may operate at or near theeutectic point thereof. Heat transfer may also be achieved via alloytransformations in solid-liquid eutectic mixtures and in eutectic moltensalts.

Referring to FIG. 4, in another approach heat exchanger 200 may provideheat to a circulating heat exchange fluid 310. The circulating heatexchange fluid may include water, steam, super-heated steam, and ahydrocarbon heat transfer fluid. In one embodiment the hydrocarbon heattransfer fluid is part of a hot oil loop used for carrying heat to otherunit operations in zone 300 by stream 320. Hot oil loops may be used forproviding high temperature heat to process users in applications wherefired heaters are not appropriate. Conventionally, the so called hot oilis circulated in a loop that includes a fired heater to supply heat tothe heat transfer fluid and process which use heat. In accordance withthis approach, the fired heater in the conventional hot oil loop wouldbe replaced by the heat exchanger 200 recovering heat from one of thepyrolysis stream and the effluent stream. The heat exchanger fluid forthe hot oil loop may be a synthetic heat transfer fluid which ishydrocarbon fluid that is specially designed to be thermally stable or anon-synthetic heat transfer fluid. Examples of commercially availablesynthetic heat transfer fluids include, for example, Therminol 66 bySolutia, Dowtherm RP by Dow, and Marlotherm SH by Sasol. Examples ofnon-synthetic heat transfer fluids include for example diesel fuel orheavy gas oil or any other suitable hydrocarbon stream commonlyavailable and known in the art. The hot oil from heat exchanger 200 maybe circulated to process users in zone 300 to provide heat directly orto a boiler to produce steam which in turn may be used to generateelectricity, drive compressors, provide heat to process users, or anyother use of steam known in the art.

In another approach, the heat exchange fluid may be water and preferablywater preheated to its bubble point. In this approach, steam is raiseddirectly from the pyrolysis stream or effluent stream in heat exchanger200. Advantageously, this directly produces steam, which may be used inother unit operations as described above. In addition, the circulatingwater rate may be set to minimize the temperature rise of the heattransfer fluid such that saturated steam is produced. In addition, thewater may be provided from one or more cooling channels incorporatedinto reactor 5 for the purpose of cooling the reactor vessel walls. Thewater may be preheated in the said channels, but not vaporized. Thepreheated water from the cooling channels may then be directed to heatexchanger 200 to produce steam. The pressure of the circulating watermay be increased or reduced as desired to maximize steam production atthe desired temperature and pressure.

Referring to FIG. 7, in one approach, heat exchanger 200 consists of aseries of two or more heat exchangers 200 and/or steam drums 400 toproduce steam of varying grades. Each heat exchanger in series willproduce lower pressure, lower grade steam than the upstream exchangersand steam drums. For example high pressure steam 410 at 600 psig, mediumpressure steam 420 at 150 psig, and low pressure steam 430 at 50 psig.The grades of steam may be optimized to produce power, as heat exchangemedia, or drive other process operations such as a compressor, aturbine, or any combination thereof as desired and understood by oneskilled in the art in zone 300. The steam may be provided in a stream toa power generation device 440 or other process operation. The condensatefrom the various process users in zone 300 may be recycled back to thecooling channels of reactor 5 or heat exchanger 200 via line 450. In yetanother approach, the heat exchange fluid directed to heat exchanger 200is steam which is superheated in the subject heat exchanger. The steammay be produced by one of a series of heat exchangers 200 as describedabove or provided from elsewhere in the process.

In yet another approach, the fluid heated in heat exchanger 200 may beselected from process streams available in the process described withregard to FIG. 1 and FIG. 2. For example one or more of the fuel andoxygen injected into combustion zone 25 via nozzle(s) 30 and feedstockprovided to the reactor 5 via feedstock inlet 40 may be preheated in oneor more heat exchangers 200 of FIG. 3. Preheating the fuel, oxygen, andfeedstock as described above will improve the efficiency of the methanepyrolysis reactor by decreasing the amount of fuel that needs to beburned to achieve a desired level of conversion. In this way heat may beprovided directly to the process streams rather than to a utilitystream.

In one example, the reactor effluent stream after pyrolysis in thesupersonic reactor 5 has a reduced methane content relative to themethane feed stream ranging from about 15 mol-% to about 95 mol-%. Inanother example, the concentration of methane ranges from about 40 mol-%to about 90 mol-% and from about 45 mol-% to about 85 mol-% in anotherexample.

In one example the yield of acetylene produced from methane in the feedin the supersonic reactor is between about 40% and about 95%. In anotherexample, the yield of acetylene produced from methane in the feed streamis between about 50% and about 90%. Advantageously, this provides abetter yield than the estimated 40% yield achieved from previous, moretraditional, pyrolysis approaches.

By one approach, the reactor effluent stream is reacted to form anotherhydrocarbon compound. In this regard, the reactor effluent portion ofthe hydrocarbon stream may be passed from the reactor outlet to adownstream hydrocarbon conversion process for further processing of thestream. While it should be understood that the reactor effluent streammay undergo several intermediate process steps, such as, for example,water removal, adsorption, and/or absorption to provide a concentratedacetylene stream, these intermediate steps will not be described indetail herein.

Referring to FIG. 2, the reactor effluent stream having a higherconcentration of acetylene may be passed to a downstream hydrocarbonconversion zone 100 where the acetylene may be converted to form anotherhydrocarbon product. The hydrocarbon conversion zone 100 may include ahydrocarbon conversion reactor 105 for converting the acetylene toanother hydrocarbon product. While FIG. 2 illustrates a process flowdiagram for converting at least a portion of the acetylene in theeffluent stream to ethylene through hydrogenation in hydrogenationreactor 110, it should be understood that the hydrocarbon conversionzone 100 may include a variety of other hydrocarbon conversion processesinstead of or in addition to a hydrogenation reactor 110, or acombination of hydrocarbon conversion processes. Similarly, unitoperations illustrated in FIG. 2 may be modified or removed and areshown for illustrative purposes and not intended to be limiting of theprocesses and systems described herein. Specifically, it has beenidentified that several other hydrocarbon conversion processes, otherthan those disclosed in previous approaches, may be positioneddownstream of the supersonic reactor 5,including processes to convertthe acetylene into other hydrocarbons, including, but not limited to:alkenes, alkanes, methane, acrolein, acrylic acid, acrylates,acrylamide, aldehydes, polyacetylides, benzene, toluene, styrene,aniline, cyclohexanone, caprolactam, propylene, butadiene, butyne diol,butandiol, C2-C4 hydrocarbon compounds, ethylene glycol, diesel fuel,diacids, diols, pyrrolidines, and pyrrolidones.

A contaminant removal zone 120 for removing one or more contaminantsfrom the hydrocarbon or process stream may be located at variouspositions along the hydrocarbon or process stream depending on theimpact of the particular contaminant on the product or process and thereason for the contaminants removal, as described further below. Forexample, particular contaminants have been identified to interfere withthe operation of the supersonic flow reactor 5 and/or to foul componentsin the supersonic flow reactor 5. Thus, according to one approach, acontaminant removal zone is positioned upstream of the supersonic flowreactor in order to remove these contaminants from the methane feedstream prior to introducing the stream into the supersonic reactor.Other contaminants have been identified to interfere with a downstreamprocessing step or hydrocarbon conversion process, in which case thecontaminant removal zone may be positioned upstream of the supersonicreactor or between the supersonic reactor and the particular downstreamprocessing step at issue. Still other contaminants have been identifiedthat should be removed to meet particular product specifications. Whereit is desired to remove multiple contaminants from the hydrocarbon orprocess stream, various contaminant removal zones may be positioned atdifferent locations along the hydrocarbon or process stream. In stillother approaches, a contaminant removal zone may overlap or beintegrated with another process within the system, in which case thecontaminant may be removed during another portion of the process,including, but not limited to the supersonic reactor 5 or the downstreamhydrocarbon conversion zone 100. This may be accomplished with orwithout modification to these particular zones, reactors or processes.While the contaminant removal zone 120 illustrated in FIG. 2 is shownpositioned downstream of the hydrocarbon conversion reactor 105, itshould be understood that the contaminant removal zone 120 in accordanceherewith may be positioned upstream of the supersonic flow reactor 5,between the supersonic flow reactor 5 and the hydrocarbon conversionzone 100, or downstream of the hydrocarbon conversion zone 100 asillustrated in FIG. 2 or along other streams within the process stream,such as, for example, a carrier fluid stream, a fuel stream, an oxygensource stream, or any streams used in the systems and the processesdescribed herein.

While there have been illustrated and described particular embodimentsand aspects, it will be appreciated that numerous changes andmodifications will occur to those skilled in the art, and it is intendedin the appended claims to cover all those changes and modificationswhich fall within the true spirit and scope of the present disclosureand appended claims.

1. An apparatus for producing acetylene from a feed stream comprisingmethane comprising: a supersonic reactor for receiving the methane feedstream and heating the methane feed stream to a pyrolysis temperature toproduce an effluent; a reactor shell of the supersonic reactor fordefining a reactor chamber; a combustion zone of the supersonic reactorfor combusting a fuel source to provide a high temperature carrier gaspassing through the reactor space at supersonic speeds to heat andaccelerate the methane feed stream to a pyrolysis temperature; and aheat exchanger for transferring heat from at least a portion of at leastone of a pyrolysis stream and an effluent stream to at least one otherportion of the process stream.
 2. The apparatus of claim 1, wherein theheat exchanger comprises a ceramic tube heat exchanger.
 3. The apparatusof claim 2, wherein the ceramic tube comprises a material selected fromthe group consisting of a carbide, a nitride, titanium diboride, asialon ceramic, zirconia, or thoria.
 4. The apparatus of claim 1,wherein the heat exchanger includes coated highly-inert tubes torestrict corrosion thereof.
 5. The apparatus of claim 4, wherein thecoated highly-inert tubes include highly-sulfided tubes.
 6. Theapparatus of claim 4, wherein the coated highly-inert tubes includecarbon-coated tubes.
 7. The apparatus of claim 1, wherein the heatexchanger comprises a superalloy tube heat exchanger.
 8. The apparatusof claim 7, wherein the superalloy tube heat exchanger comprises atleast one of nickel-based high-temperature low creep superalloy andchromium.
 9. The apparatus of claim 1, wherein the heat exchangerprovides heat to a circulating heat exchange fluid.
 10. The apparatus ofclaim 9, wherein the circulating heat exchange fluid comprises a fluidselected from the group consisting of water, steam, super-heated steam,and a hydrocarbon heat transfer fluid.
 11. The apparatus of claim 10,further comprising a hot oil loop, and wherein the circulating heatexchange fluid comprises a hydrocarbon heat transfer fluid providing atleast a portion of the hot oil loop.
 12. The apparatus of claim 9,wherein the heat exchange fluid comprises water preheated to its bubblepoint.
 13. The apparatus of claim 1, wherein the heat exchangercomprises a plurality of heat exchangers in series to produce steamstreams of varying grades.
 14. The apparatus of claim 13, furthercomprising a power generation device, and wherein at least one steamstream is provided to a power generation device to generate powertherefrom.
 15. The apparatus of claim 1, wherein the heat exchanger is astab-in heat exchanger with a heat transfer fluid flowing therethrough.16. The apparatus of claim 15, wherein the heat transfer fluid isselected from the group consisting of molten metal, VSO heat exchangerfluid, raising steam, superheating steam, hot oil, and liquid sodium.17. The apparatus of claim 1, wherein the heat exchanger includes aphase transformation fluid capable of transferring energy from portionsof the effluent stream.
 18. The apparatus of claim 1, wherein the heatexchanger fluid includes undergoes a transformation, including at leastone of a eutectic-eutectic fluid transformation and eutecticsolid-liquid transformation of a composition for transferring energyfrom the portion of the effluent stream.
 19. An apparatus for producingacetylene from a feed stream comprising methane comprising: a supersonicreactor for receiving the methane feed stream and heating the methanefeed stream to a pyrolysis temperature to produce an effluent; a reactorshell of the supersonic reactor for defining a reactor chamber; acombustion zone of the supersonic reactor for combusting a fuel sourceto provide a high temperature carrier gas passing through the reactorspace at supersonic speeds to heat and accelerate the methane feedstream to a pyrolysis temperature; and a heat exchanger for transferringheat from at least a portion of at least one of a pyrolysis stream andan effluent stream.
 20. The apparatus of claim 19, wherein the heatexchanger comprises a transport bed heat exchanger with direct contactbetween the at least one of the pyrolysis stream and the effluent streamand a bulk solid.
 21. The apparatus of claim 19, wherein the heatexchanger comprises a transport bed heat exchanger with indirect contactbetween the at least one of the pyrolysis stream and the effluent streamand a bulk solid through a component of the heat exchanger.
 22. Theapparatus of claim 19, wherein the heat exchanger includes a hightemperature thermoelectric heat exchanger for generating electricity